DIAMOND DIES FOR DRAWING OF COPPER WIRE 



25 



noticed wiiere the line copper particles liave been compacted by the heat and 

 pressure to form a solid conical mass which has welded to the wire. Deep 

 grooves in the reduction angle and bearing invariably follow back to the 

 pressure ring or irregularities in the die surfaces in which the metal particles, 

 dirt, etc. have lodged. 



Characteristic of copper and other non-ferrous metals is its ready flow 

 under pressure such as is present in the die reduction angle. This condition 

 causes die packing, metal galling and the resultant wire scoring to take place 

 at surprisingly slight irregularities in the die drawing surfaces. This is 

 particularly true at high drawing speeds due to the rapid lineal movement 

 of the wire surfaces. Again this emphasizes the necessity for a high polish. 

 The harder ferrous metals tend to bridge across these small irregularities 

 rather than to flow into them. 



Highly polished surfaces free from scores, traces of ripping rings and 

 scratches are desired." All the die surfaces with the exception of the relief 



Table I 



angle and top flare of the bell should be so finished. The polished surfaces 

 should be a smooth curve as undulating surfaces are undesirable. 



Dies after full use to oversize will retain their original high polish if no 

 breaks in the stone, i.e. chips, cracks, etc. have occurred. This polish will 

 also be present in the wear eroded areas. 



Pounds Pull to Draw the Wire through the Die 



Die pull has long been known to the trade as a factor which greatly 

 influences wire drawing operations. However, it has not been customary 

 to recognize its relation to the drawing die itself and it has not been applied 

 as an everyday simple means of checking a die's possible performance. The 

 Western Electric Company has considered for a long time this die charac- 

 teristic in its wire drawing developments* and practical values for use in the 

 present high-speed drawing machines have been established. Listed in 

 Table 1 are the values used for these dies. It should be added that, while 

 die pulls are important, these are not critical and a deviation of +10% can 

 be used but this would result in greater power consumption and more 



